This invention relates to electric motor structure and more particularly to an improved electric motor ventilation structure wherein a rotor shaft mounted "pull through" fan is associated with a motor endshield defined air circulating chamber adjacent the stator and rotor assembly of an electric motor to cause circulating air to break the "hot" boundary layer of air immediately adjacent the motor windings.
It is known in the art of electric motor structure to generally circulate air over the rotor and stator assembly of an electric motor to regulate motor winding temperature. Various motor housing designs have been provided to allow air to enter into the motor housing with or without the use of air movers to provide cooling air into the housing so as to pass over and ventilate the stator and rotor windings. For the most part, these past motor housing designs have proven to be costly in manufacture and assembly often failing to provide adequate heat flow from the motor windings to the introduced air and appropriate removal of the heated air from the housing. For example, internal fan blades mounted to end rings on the rotor have been utilized to create a positive pressure flow within the motor housing but the manufacture and assembly has been comparatively costly and the positive air circulating pressure within the motor housing has not avoided the aforementioned heat flow shortcomings.
In accordance with the present invention, a novel ventilating structure for electric motors is provided which recognizes the importance of obtaining proper mass heat flow transfer from the stator and rotor assembly by removing or at least breaking the "hot" boundary layer of air which exists in close proximity to the windings, the inventive structure providing a "pull through" ventilating structure which ensures increased air flow and increased air velocity over and proximate the windings. Further, the structure of the present invention provides a negative pressure within a surrounding chamber proximate the stator and rotor assembly to produce effective continuous flow through of the circulating air and mass heat transfer during motor operations. Moreover, the structural arrangement of the present invention utilizes a novel endshield arrangement in accomplishing this desired ventilation and at the same time rotatably journalling the rotor shaft relative the stator. In addition, the novel, straightforward, and comparatively inexpensive to manufacture and assemble structure of the present invention provides a unique external fan arrangement which can be effectively and efficiently assembled and held in proper operating position on the rotor shaft extending from the stator and rotor assembly of the electric motor.
Various other features of the present invention will become obvious to one skilled in the art upon reading the disclosure set forth herein.